Description

The systemUsage memory limit is triggered and the pending message cursor for non persistent messages is flushing its in memory cache to temp store, this is taking a long time and in the mean time, other cursors that need to flush to disk are blocking on the temp store, and other sends to that destination are blocked. In this scenario, the broker should come back to life once the flush completes

From user:

First of all, the situation you describe is IMHO worth some log messages (probably one when "swapping" starts and one when it ends).
With these, one can see how long the broker is blocked this way and how frequently this happens.